This invention relates generally to couplings and, more particularly, to an improved insulated coupling for a television tuner shaft or the like.
Several techniques for providing an insulated shaft coupling are known. The most common technique utilizes a two section metal shaft having an axially extending chamber formed in the end of one of the sections and an axially extending reduced diameter section formed in the other section. An insulating bushing is inserted into the chamber, and the reduced diameter portion of the other metal section is pressed into the bushing which serves to hold the two sections together with a press fit.
Although this system provides a way to insulate two sections of a metal shaft, the system necessitates a compromise between the insulating qualities and the mechanical strength of the coupling. For example, when such a prior art system is employed in a television tuner shaft having a nominal 0.250 inch diameter, the reduced diameter section of the mating section must be reduced to approximately 0.150 inch to permit the walls of the insulating bushing to be sufficiently thick to provide the necessary insulating properties. Unfortunately, reducing the diameter of the shaft within the coupling reduces the mechanical strength of the shaft and results in bending and breakage problems occurring at the coupling, particularly with long shafts of the type commonly used in console television sets.